Our data showed that the specificity for MTBC was 100% in all but the rrs subassay, due to the highly conserved nature of the locus. Since the IS6110 subassay has 100% specificity for MTBC with the highest sensitivity, it serves as a gatekeeper for validity checks of rrs results; the rrs results can be considered valid only when the IS6110 subassay yields positive results for MTBC. Therefore, the impact of the decreased specificity of the rrs subassay is minimized.